Re: [PATCH v5 0/6] arm64: arch_timer: Add workaround for hisilicon-161601 erratum

[Hanjun Guo <guohanjun@huawei.com>]

Hi Ding,

On 2016/12/23 15:04, Ding Tianhong wrote:
> Erratum Hisilicon-161601 says that the ARM generic timer counter "has the
> potential to contain an erroneous value when the timer value changes".
> Accesses to TVAL (both read and write) are also affected due to the implicit counter
> read.  Accesses to CVAL are not affected.
>
> The workaround is to reread the system count registers until the value of the second
> read is larger than the first one by less than 32, the system counter can be guaranteed
> not to return wrong value twice by back-to-back read and the error value is always larger
> than the correct one by 32. Writes to TVAL are replaced with an equivalent write to CVAL.
>
> v2: Introducing a new generic erratum handling mechanism for fsl,a008585 and hisilicon,161601.
>     Significant rework based on feedback, including seperate the fsl erratum a008585
>     to another patch, update the erratum name and remove unwanted code.
>
> v3: Introducing the erratum_workaround_set_sne generic function for fsl erratum a008585
>     and make the #define __fsl_a008585_read_reg to be private to the .c file instead of
>     being globally visible. After discussion with Marc and Will, a consensus decision was
>     made to remove the commandline parameter for enabling fsl,erratum-a008585 erratum,
>     and make some generic name more specific, export timer_unstable_counter_workaround
>     for module access.
>     
>     Significant rework based on feedback, including fix some alignment problem, make the
>     #define __hisi_161601_read_reg to be private to the .c file instead of being globally
>     visible, add more accurate annotation and modify a bit of logical format to enable
>     arch_timer_read_ool_enabled, remove the kernel commandline parameter
>     clocksource.arm_arch_timer.hisilicon-161601.
>
>     Introduce a generic aquick framework for erratum in ACPI mode.
>
> v4: rename the quirk handler parameter to make it more generic, and
>     avoid break loop when handling the quirk becasue it need to
>     support multi quirks handler.
>
>     update some data structures for acpi mode. 
>
> v5: Adapt the new kernel-parameters.txt for latest kernel version.
>     Set the retries of reread system counter to 50, because it is possible 
>     that some interrupts may lead to more than twice read errors and break the loop,
>     it will trigger the warning, so we set the number of retries far beyond the number of
>     iterations the loop has been observed to take.
>
> Ding Tianhong (4):
>   arm64: arch_timer: Add device tree binding for hisilicon-161601
>     erratum
>   arm64: arch_timer: Introduce a generic erratum handing mechanism for
>     fsl-a008585
>   arm64: arch_timer: Work around Erratum Hisilicon-161601
>   arm64: arch timer: Add timer erratum property for Hip05-d02 and
>     Hip06-d03
>
> Hanjun Guo (2):
>   arm64: arch_timer: apci: Introduce a generic aquirk framework for
>     erratum
>   arm64: arch_timer: acpi: add hisi timer errata data

Since the ACPI code is conflict with Fuwei's GTDT patch set, let's split this patch
set into two parts, one is the DT based code, and the other is the ACPI part,
I will rebase ACPI code on top of Fuwei's patch set so please go upstream first.

Thanks
Hanjun